Direct reading multifrequency generator



R. E. COLANDER DIRECT REAEGMULTEEEQUEEf GENERATOR 2 Sheets-Sheet l Filed Dec.

IIII IN VEN TOR. POV a/V05? July 19, 1949. R. E. coLANDER DIRECT READING MULTIFREQUENCY GENERATOR 2 SheetsFSheet 2 Filed DeO. 30, 1947 INVENTOR. /Pw/ ,/5 @aA/vof@ BY j/j @T7-OP Patented July 19, 1949 DRECT READING MULTIFREQUENCY GENERATOR Roy 'Clanden Boulder, Colo., assigner to Cllins Radio Company, Cedar Rapids, Iowa, a corporation yof Iowa Application December 30, 1947, Serial No. 794,509

16 Claims.

This invention relates to frequency generators and more especially Vto so-called signal generators such as are used in radio testing, calibrating and the like.

A principal object of the invention is to provide an improvedarrangement for selectively setting the output frequency of an oscillator, and for simultaneously and automatically indicating the selected frequency.

Another object is to provide a direct reading frequency generator which can be used with a replaceable oscillator without disturbing the accuracy of the frequency indication. y

Another object is to provide an adjustable frequency generator of the direct reading type wherein there is avoided the necessity of employing tuning arrangements for the oscillator which would normally have to be of linear characteristic or of some other known or definite characteristic.

A feature of the invention relates to a direct reading frequency indicator arrangement for signal generators, whereby the indications are produced as a composite numerical indication on a conventional rotatable dial counter and upon a calibrated frequency meter.

Another feature relates to a direct reading frequency indication arrangement for signal generators and the like, employing a counter of the cumulative digit dial type for indicating a coarse frequency setting, and a frequency calibrated meter for indicating the interpolated or ne frequency settings, in conjunction with a spectrum generator which produces a series of uniformly spaced frequency check points and a cooperating special frequency detection circuit for `controlling the operation of the counter and meter in response to Variable settings of the oscillator.

A further feature relates to the novel organization, arrangement and relative interconnection of parts which cooperate to provide an improved direct reading signal frequency generator.

In the drawing which shows, by Way of example, certain preferred embodiments,

Fig. 1 is a composite schematic circuit and block diagram of a system according to the invention. v

Fig. 2 is a graph explanatory of the operation of Fig. 1.

Fig. 3 is an enlarged detailed view of the frequency meter of Fig. 1. v

Fig. 4 is a sectional view of Fig. 3, taken along the lines 4--l thereof. l

Fig. 5 is a modification of Fig. 3.

Referring to Fig. l, there is represented by the,

block I, any well-known oscillator such as is customarily employed in 'signal generators. It may comprise, for example, a grid-controlled electron tube having a tuning circuit with one or more adjustable elements for changing the oscillator frequency over the desired range in continuous frequency increments. Merely for illustration, it will be assumed that the oscillator l is to cover the range of 2500 kilocycles to 7500 kilocycles. The tuning element of oscillator l is provided with a manually Asettable knob 2 which is coupled through a suitable Slip friction clutch 3 to a forward-reverse switch 4, comprising for example a disc 5 having a peripheral knob 6 which registers with the operating switch arm 1 of a single-pole double-throw toggle switch. Thus, when knob 2 is turned clockwise to increase the frequency of oscillator it operates arm 'I to close with contact 8. lThe arm 1 then acts as a stop to limit any further rotation of disc 5, but allowing the knob 2 to be continuously rotated. The switch arm 1 is connected over conductor 9 to the normally open contacts I0, Il, of an electromagnetic relay switch I2. Contacts I0, Il, when closed, as will be described, complete a circuit over conductors l91, I3, I4, I5, Aand the contacts 'l and 8 to the winding I6 of the forward stepping mechanism associated With the dial counter l'l. This counter may be of any wellkncwn type comprising, for example, a tens dial I8, a hundreds dial I9'. a thousands dial 20. The dial I 8 is calibrated in 10 equally spaced markings from 00, 10 90, and is rotatable in a step-by-step manner to indicate these successive 10 kilocycle steps. The dials I9 and 20 are cumulative and decumulative with respect to the rotation of dial I8, thus for each successive ten steps of dial I8 in one direction, the dial I9 is rotated one step in the same direction. Likewise, for each ten successive steps of dial I9, the dial 20 is rotated one step. Since numerical counter mechanisms of this type are well-known in the art,- detailed description thereof is not necessary herein. Under the above assumed range for oscillator I which has a lower frequency of 2500 kilocycles,` the normal or lowermost setting of the counter I1 will be at 2500.

The reverse or decumulative rotation of counter I 'l is controlled by a reverse stepper device the circuit of whose control magnet 2| is controlled by means of switch contacts 1, 22, and the contacts I0 and Il, by way .of conductors 9 and 23. The relay I2 which controls the ten successive kilocycle steps of dial I8 is controlled by a zero beat requency detector 34. For this purpose,

there is provided a spectrum generator 25 of any 1 quencies spaced kilocycles apart which pro-I vide check points for the oscillator I, as well as' providing automatic control signals for the coun- 1 ter I1 and for the frequency meter 28 and its associated mask control mechanism 29 as will be described. For example, l the 4multi-vibrator ,25,`

may produce a frequency spectrum which includes frequencies 2500 kilocycles, 2510 kilocycles, 2520 kilocycles, etc., up to the upper limit of the oscillator I. For a detailed description-of such a multi-vibrator frequency spectrum generator., reference may be hadA to any standard handbook on electronics, e. g., Radio Engineers Handbook, by F. E Terman, f The output of oscillator. I is supplied to any suitable load device 30. A portion of this output is also supplied to lany well-known beat detector v3l to which is also supplied the signals from generator 25. For a detailed description of such a beat detector, reference maybe had toRadio Engineers Handbook, by Tberman. The output ofv detector 3I.therefore consists of an audio frequency voltage.v Thus, when the signal from oscillator I coincides with therfrequency of a check point from generator25, e. g., 2520 kilocycles, the beat frequencyfrom detector 3I is zero.V When the frequency of oscillator I is midway between two successive check points of generator 25, e, g., 2525 kilocycles, the beat frequency from detector 3| is 5000 cycles. As the fre-'- quency of oscillator I is varied over the rst half ofthe interval between successive check points 'for example between 2520 kilocycles and 2525 kilocycles, the frequency of the beat note correspondingly increasesflinearly between Zero and 5000 cycles; while during the second half of this same interval, for example 2525 to 2530 kilocycles, the beat note correspondingly decreases linearly from 5000 cycles to zero. This relation is clearly illustrated in the graph of Fig. 2, wherein four successive check `points are illustrated. The audio frequency beat note voltage from detector 3I is amplified in a suitable audio frequency amplier 32 which Yis preferably of the `direct coupled type so as to amplify the entire range between Zeroand 5000 cycles. The output of amplifier 32 is supplied in tandem to three separate circuits 33, 34, 35. Y Cir-- cuit 33 is an audio frequency measuring circuit which produces inb'its output a voltage which is proportional tothe frequency of the input supplied to it from amplifier 32. For example, any well-known frequency discriminator circuit or electronic frequency counter circuit may be used for the device V33. The output of circuit 33 is applied to any suitable meter 28 whose scales are calibrated in cycles per second. One of these scales reads from zero to 5000 cycles per second in a forward or clockwise direction as illustrated in Fig. 3, and the other scale is calibrated in a `reverse of counterclockwise direction from 5000 cyclesY to 10,000 cycles. This meter has a shiftable mask 36 having a window 31, the mask being arranged for upward-and downward movement to expose only one of the scales at a time.

cam 38 which is adapted to be rotated ina stepby-step manner by the usual driving pawl 39 controlled by a suitable solenoid 40. For this purpose, the mask 36 carries a post or cam follower 4I which, through suitable leverage arrangements, engages theV teeth of wheel 38. In Fig. 3, the -wheel 38 is shown insuch aY position that the mask 36 is in'its downward position exposing the 0-5000 scale. When the wheel 38 is moved one step under control of solenoid 40, the mask is raised so that the window 31 exposes only the 10,000-5,000 scale. When the wheel 38 has been moved one step, the mask 36 remains in its correspondinglyvset position until the solenoid 40 receives another operating imy pulse.

The'meter is of course provided with a pointer 4 2 and with the usual meter coils for swinging the pointer across the scales in proportion to the voltage from circuit 33. Thus, there is provided at all times'` a continuous indication of the frequency difference `between oscillator I and the nextlower frequency check point from generator T-he 'second circuit 34 is a zero frequency detector of any well-known type such for example ment combined with a trigger circuit. Itmay consist for example of a suitableiilter circuit and The upward and downward positioning of mask 36 is Vcontrolled by a toothedwheel or toothed amplifier which produces an output impulse only when `zeroV frequency isapplied to its input, so as to operate theV relayIZ. Relay I2'hasan additional set of contacts 43, 43a which, whenY closed, complete the energizing circuit for solenoid 40, Thus, each instant the oscillator I is tuned to the same frequency as a check point frequency of generator 25, e g., 2520 kilocycles, the relay I2 operates to cause the upper scale (0-5000) on the meter '28 to be exposed. Likewise, each time thevzero beat condition occurs as the oscillatoi` I passes successive check pointsv 2500, 2510, etc., an impulse is applied to the proper unit II-Y or 2I depending upon the direction in which the knob 2 is being turned. Y

The thirdcircuit 35 is a 5000 cycle vdetector which only responds when a 5000 cycle signal is applied toits input. `For example, it may comprise an electromagneticallyl controlled reed which is tuned to 5000 cycles, although other well-known vsingle frequency selecting arrangements may be employed. When a signal appears at the output of the detector 35, it causes relay 44 to be operated. Relay 44 closes through itscontacts 45, 46, a circuit for operating the solenoid 40, whereupon the wheel 38 is rotated to present the next lowV point `of wheel 3,8 to the arm 4 I, causing the window 31 to expose the lower scale (1000G-5,000)

From the foregoing description, it will be seen that when the knob 2 is turned, for example in a clockwise direction to increase the frequency of oscillator I, 'member 5 closes contacts 1 and 8 to prepare the circuit for the' forward stepper I5. Assume for example that the oscillator I has been previously tuned to 2520.2 kilocycles, in which event the counter I1 will be registering 2520 kilocycles, and the meter 28 would indicate 200 cycles'. Also let it vbe assumed that the oscillator is now to be tuned to 2620.6 kilocycles. As the knob 2 is turned, it produces a Vcontinuously lchanging beat in the output of device 3| which varies from zero to 5000 cycles which signal is continuously Yindicated on the upper scale of meter 28. When the oscillator reaches 2525 kilocyclesthe detector 35 comes into operation and causes mask 36 to blank as afsimple ampliermlow-pass filter arrange oir the -upper scale of meter 28 fand-to-expose only the lower scale, and Yat this instant the pointer t2 'is at vits full kscale deflection and'continues to -indicate v5000 cycles on the lower scale. As the oscillator progresses from 2525 kilocycles .towards v2530 kilocycles, the beat frequency current from device 3-I decreases in frequency causing the .pointer 42 to move down scale, which scale however is calibrated in reverse direction, thus lcor- :rectly and continuously indicating the frequency in cycles per second. When the oscillator reaches the 2530 klocycles check point, a zero beat frequency lappears at the input Aof detector 34, causing relay I2 to operate. Relay vI2 then causes the mask 36 to be restored to its lower position to yexpose the upper scale (0-5000) of the meter 28 and at the same time it causes the forward stepper .i6 to advance the dial I8 of `counter II Ione step to indicate 2530. The above sequence of QD- -erations is repeated as the oscillator I passes through successive check points until finally the counter I'I indicates the desired frequency of 2620, and the meter 28 indicates 600 cycles.

i The foregoing arrangement provides a convenient means by which the final selected frequency setting of oscillator 21 can be read in coarse increments on the `counter FI in kilocycles, and the line increments in cycles per second can Abe read on meter 28. It eliminates the necessity for providing a linear `or some other definite tuning characteristic for the oscillator, the only `requirement being that the oscillator I have goed frequency stability. It is possible with this arrangement simply to substitute another oscillator for the oscillator I Without aifecting the accuracy of the indication. Thus, this other oscillator can beset to the frequency indicated by the counter II'i and then inserted into the circuit. Thereafter, the system would continuously indicate frequency as the new oscillator is tuned, in the manner above described.

Instead of employing a movable mask to expose the two scales of the meter 28, an arrangement such as shown in Fig. 5, may be employed. In this case, the scales are in the form of transparent markings on an otherwise opaque member 41. Located in back of each of the scales is a corresponding electric lamp bulb 48, 49, each bulb lighting up only its corresponding scale. In this arrangement, the arm 4I when in its lower position as shown in Fig. 5, closes a circuit from the current supply terminals 50 to lamp i9. When the arm lli is riding on a high point of the wheel 38, the current is supplied only to the lamp 48.

Various changes and modifications may be made in the disclosed embodiments without departing from the spirit and scope of the invention.

What is claimed is:

1. A frequency generating arrangement, comprising an oscillator to be tuned to any desired frequency throughout a predetermined range, a frequency spectrum generator for producing equally-spaced frequency check points distributed throughout said range, and circuit arrangements and frequency-indicating means controlled by the combined frequency outputs of said oscillator and said generator for producing continuous numerical indications of the oscillator frequency as it is being tuned to different frequencies in said range, said circuit arrangements including a beat frequency detector for producing an audio frequency beat signal which varies between successive zero beats which zero beats correspond to the tuning of the oscillator between successive check points from .said spectrum generator, and means controlled 1by1said nbeat signals for producing 'a coarse 4:numerical indication representing said ycl'ieck points, :and ra separate ne numerical indication representing the incremental frequency setti-ng .of said oscillator vas it is being tuned between said successive check points.

A frequency generating arrangement, comprising an oscillator to be tuned to any desired frequency throughout a `predetermined range, a frequency spectrum .generator for producing :equally-spaced frequency cheek points distributed throughout said range, circuit arrangements and frequency-indicating means controlled by the combined frequency outputs of said 'oscillator and said 'generator for producing continuous numerical indications of the oscillator frequency as it is being tuned to different frequencies in said range, said indicator means comprising a numerical dial counter device for indicating the successive check points of lsaid spectrum generator, and a calibrated .indicating meter for indicating the incremental fi'equcncies between successive check points.

3. A frequency generating arrangement, comfan 'oscillator to be tuned to any 'desired frequency throughout a predetermined range, va frequency spectrum generator for producing equally-spaced frequency check points v'distribute-d throughout said range, circuit arrangements land frequency-indicating means controlled by the combined frequency outputs o1 said oscillator and said generator for producing continuous numerical indications of the oscillator frequency 1asit is being 'tuned to different frequencies in said range, said indicator means including callbrated frequency meter arrangements for indicating oscillator frequencies between suees-sive check points, said meter having a pair of scales,

one scale 4covering one portion of the frequency range between successive check points and the other scale covering the remaining portion of said range between said successive check points', and means responsive to the tuning of said .oscillator throughout said range for automatically rendering only the proper one of said scales effective for indica-tion purposes.

4. A direct reading frequency generating arrangement comprisng an oscillator to be tuned to any desired frequency throughout a predetermined range, a frequency spectrum generator for simultaneously producing frequency check points equally 'distributed throughout said range, means to produce a beat note signal representing the frequency difference between said oscillator and said spectrum generator which signal continuously increases in frequency from zero to a maximum and then from said maximum back to zero between successive check points, a, frequency counter device, a frequency meter device, means to apply said beatl note signal to control the setting of .said meter device, a Zero beat frequency detector device, and means controlling the said coun-ter device by the output of said zero beat detector device.

5. A direct reading frequency generating arrangement accord'mg to claim 4 in which said frequency meter device comprises two separate frequency -indicating scales each calibrated throughout a different portion of the range between successive check points, and means are provided for rendering the correct scale effective and autor-naticallyl in response to the presence of said maximum beat frequency.

6. A direct reading frequency generating arvrangement according to claim 4 in which said =frequency meter device comprises two separate Yfrequency-indioating s-cales, lone scale bemg calisuccessive check points and then continuously decreases from said maximum to zero as said oscillator is being tuned between successive check points.

8. A direct reading frequency generating arrangement according to claim 4 in which said .counter device is provided with forward and reverse actuators, and switch means are provided for selectively rendering one of said actuators Y 'effective in accordance with the direction of tuning of said oscillator to increase the oscillator frequency, and for selectively rendering the other Vactuator effective in accordance with the tuning of said oscillator to decrease its frequency.

9. A direct reading frequency generating arrangement according to claim '4 in which saidv oscillator has a tuning knob which is coupled to a two-position switch for operating said switch to either position in laccordance with the direction of turning of said knob, and said counter device is provided with forward and reverse actuators which are rendered selectively effective by said Y switch.

10. A frequency generating arrangement ac-` cording to claim 4 in which said oscillator has -a tuning knob which is coupled to a two-position switch to operate said switch to either position in accordance with the direction of turning ofV said knob, and said counter device is provided with forward and reverse actuators, and means are provided for selectively rendering said actua-tors effective under control of said switch and under control of the output of said zero beat fre quency detector. Y

11. A direct reading signal generator for radio apparatus and the like, comprising an oscillator to be tuned to any desired frequency throughout a predetermined range, a frequency spectrum generator for simultaneously producing frequency check points equally distributed throughout said range, a numerical counter device for cumulatively indicating the frequency ofthe os'- cillator as it is successively tuned through said check points, a frequency-calibrated meter for Y indicating the increment-al frequency Ichange of the oscillator as it is being tuned from one check point to the next check point, a beat detector excited by the oscillator frequency and the spe-ctrum generator frequency, a frequency-measuring device connecting said beat detector to said meter, a zero beat frequency detector controlled by the output of said beat detector, and relay switch means controlled by said zero beat detector for controlling the actuation of said numerical counter.

12. A direct reading signal generator according to claim 11 in which said numerical counter device is provided with forward and reverse actuators, and said oscillator is provided with a tunning knob, said knob being coupled to a twoposition switch which is arranged to assume one position when said knob is rotated in one direction and to l'assume another position when said knob is rotated in the opposite direction, and respective operating circuits are provided for said actuators which operating circuits Vare selectively controlled byrsaidtwo-position switch.

13. A direct reading signal generator .according to claim 11 in which said frequency-measuring device comprises a meter having a pair of scales each calibrated over a different portion of the frequency range between suc-cessive check points from said spectrum generator, a shiftable mask for rendering only one of said scales effective.V

and means Controlled by the output of 4said zero beat frequency detector for selectively operating said mask.

14. A direct reading signal generator according to claim 11 in which said frequency-measuring device comprises a meter-'having two separate scales, one calibrated forwardly over half the frequency range between successive check points from the spectrum generator and the other scale calibrated reversely over the remaining half of the said frequency range between successive check points, scale control means for rendering only one scale effective, said scale control meansincluding a relay controlled by the output of said zero beat frequency detector, another detector for producing a signal when said oscillator reaches a frequencymidway between Vsuccessive check points, and another Vrelay controlled by the output of the last-mentioned detector.

15. An indicating arrangement of the char-V acter described, comprising a meter for indicating values over a predetermined range, said meter having a pair of scales, one scale being forwardly calibrated between one portion of said range, and the other scale being reversely calibrated between the remaining portion of said range, a single deflectable pointer cooperating with both scales, means Vfor automatically rendering the proper one of said scales effective, the last-mentioned means comprising a signal source whose frequency can be varied from zero to maximum representing the said one portion of said range and then from said maximum to zero to represent said remaining portion of said range, means responsive to said Vsignal to actuate said pointer, a zero beat frequency detector for producing a control voltage when said signal is at zero frequency, anV other detector for producing Ya control voltage when said signal is at said maximum frequency, and scale selector means responsive to the firstmentioned control voltage to render one scale effective and responsive to the other control voltage to render the other scale effective.

`Ah indicatingY arrangement according to 'claim 15 in which the said means for rendering the proper scale eifectivercomprises, a shiftable scale mask, a step-by-step mechanism for operating said mask, a rst relay controlled by the output of said Zero beat detector for operating said step-by-step mechanism to cause said mask to expose one of said scales, and another relay responsive to said other detector for operating said step-by-step mechanism to cause saidmask to expose the other of said scales.

' Y ROY E. COLANDER.

REFERENCES CITED UNITED STATES PATENTS Number Name Y Date Hathaway Dec. 21, 1943 

